This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-301516, filed Sep. 29, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a nucleic acid detection sensor which electrochemically detects whether a target nucleic acid chain in a test liquid has a specific base sequence.
2. Description of the Related Art
Recently, a genetic test technique with a nucleic acid chain fixed array (DNA array) is made attention as a nucleic acid detection sensor (see xe2x80x9cBeattie et al. 1993, Fodor et al. 1991, Khrapko et al. 1989, Southern et al. 1994xe2x80x9d).
DNA array indicates the array of a glass and a silicon with several cm squares where DNAs with different 101 to 105 kinds of arrays is fixed. The signed test liquid gene is reacted with a fluorescent dye and a radioisotope (RI), etc. on the array, or the unsigned test liquid gene and the compound of the sign oligonucleotide are reacted by the sandwich hybridization. When a complementary array to the DNA on the array exists in the test liquid, the signal (fluorescent intensity and RI intensity) which is derived from the sign by a specific part on the array is obtained. If the arrangement and the position of the fixed DNA are known beforehand, the base sequence which exists in the test liquid gene can be easily checked. Since a lot of information on the base sequence with the small amount sample can be obtained, DNA array is expected very much not only in the gene detection technique and also in the sequence technical (see xe2x80x9cPease et al. 1994, Parinov et al. 1996xe2x80x9d).
There are a fluorescent detection method, RI intensity detection method, and an electrochemical detection method, etc. as a technique which detects the nucleic acid which is combined with the nucleic acid detection sensor. A sign of the sample gene and a complex system are not required in an electrochemical technique. Therefore, the miniaturization of the system can be expected. In addition, since the electrode used, the electrochemical technique has an advantage that an electric reactive control can be easily performed.
Especially, among the nucleic acid detection sensors which use an electrochemical technique, the sensor having a DNA array configuration in which a plurality of electrodes where a different probe nucleic acid chain is fixed are arranged in a X-Y matrix is expected as an extremely useful technical which can detect many kinds of nucleic acids with a short time. However, the equal voltage should be applied to a lot of nucleic acid chain fixed electrodes in this sensor. Therefore, this sensor has the problems such as the circuit configuration is complex, and the response speed and accuracy are not sufficient.
An object of the present invention is to provide a nucleic acid detection sensor which can detect many kinds of nucleic acids with high-speed and high-accuracy.
A first nucleic acid detection sensor according to the present invention is characterized by comprising: a plurality of nucleic acid chain fixed electrodes to which a probe nucleic acid chain is fixed; and a counter electrode which is arranged opposite to the nucleic acid chain fixed electrode, wherein a current flowing between the counter electrode and the nucleic acid chain fixed electrode. Since the nucleic acid chain fixed electrode and the counter electrode are opposing arranged, the measurement of high accuracy can be promptly performed by the decreased amount of the test liquid.
A second nucleic acid detection sensor according to the present invention by comprising: a plurality of nucleic acid chain fixed electrodes to which the probe nucleic acid chain is fixed; a counter electrode, a current flowing between each of the nucleic acid chain fixed electrodes and the counter electrode; and a reference electrode provided for each of the nucleic acid chain fixed electrodes, configured to make a voltage between the nucleic acid chain fixed electrode and the counter electrode constant. The measurement sensitivity is improved since the reference electrode is arranged for each nucleic acid chain fixed electrode.
A the third nucleic acid detection sensor according to the present invention by comprising: a plurality of nucleic acid chain fixed electrode, to which a probe nucleic acid chain is fixed, arranged in a matrix; a plurality of scanning lines configured to select the plurality of nucleic acid chain fixed electrodes one by one; a plurality of signal lines configured to transmit a measurement signal from the plurality of nucleic acid chain fixed electrodes; a plurality of switching elements connected with the plurality of signal lines; and an A/D converter connected with the plurality of switching elements. The configuration becomes simple since only one A/D converter is prepared because the output line of the signal is shared with the switching element.